¥. 



326 DEPTHS OF THE OCEAN 



differs in various ways from Ceratittm, though systematically it 

 is not far removed from it. The cells, however, lack the brown 

 pigment-granules (at any rate, this is so in the case of marine 

 species), and the contents are pale yellow or pink. It is im- 

 probable that it can assimilate carbonic acid, and it must there- 

 fore somehow or other obtain organic matter for its nourish- 

 ment. Unfortunately nothing is known regarding its mode of 

 nourishment. These forms do not live so close to the surface 

 as the species of Ceratiuvi, but all observations made hitherto 

 indicate that they belong exclusively to parts of the sea to 

 which light penetrates, where they exist along with the other 

 algae. Their cells are much grosser than 

 those of the species of Ceratmm, and the 

 projections corresponding to the horns of 

 Ceratiuin are short or entirely wanting. 

 The membrane-curtains along the furrows 

 are only slightly developed, and the cell 

 itself is much more globular. The species 

 of Peridiniu77i, and some other genera 

 {Goiiymilax, Goniodoina), have thus at 

 best only imperfect suspension-organs, 

 but the mobility of the cells makes up for 

 „ this deficiency. The way they are formed. 



Fig. 230. • y-rr [ u 



GoNYAULAx poLYGRAMMA. too, IS dinerent from what we notice m 

 The cell-contents form a zoo- Ceratium. There is no proper cell - 



spore, shed out from the burst- ,. . , , , 11 1 • 



ing cell-wall (^1 2). (Schiitt.) Qivision, but the Cell changes its contents 

 to one, two, or four naked spores, which 

 are shed out from their original covering (see Fig. 230). Each 

 spore afterwards gradually evolves a new cell-wall for itself, 

 within which it develops as the wall expands, and bands, due to 

 accession of growth, intervene between the laminae composing 

 the structure. This has been demonstrated by Broch. The 

 genus Peridinmiu includes a large number of species distributed 

 throughout all the seas of the world, but the systematic arrange- 

 ment of the species is extremely difficult, and has not so far 

 been sufficiently investigated. A large amount of material has, 

 however, been brought home by our expedition, and it is to be 

 hoped that we shall now be able to ascertain the characteristics 

 to which we can ascribe chief systematic importance. A good 

 beginning, at all events, has been made by Kofoid and Broch. 



The family Dinophysidae possesses the most remarkable 

 suspension-organs of all the peridineae. In northern waters 

 its representatives are limited to a number of species all 



